Are you sure you really want to increment a String? The reason I ask is that if you are continually wanting to increment an integer value associated with a String it might make more sense to have an int variable and increment that.

If you really have a String and want to produce another string associated with the incremented value: use Integer.parseInt() to obtain the integer value, increment that value, and finally produce the new String with String.format().

The last step will involve something like String.format("%05d",val) but check the documentation linked to for details about the format string.